Arc mitigation devices

ABSTRACT

An apparatus includes a housing (e.g., a housing having a form factor of a molded case circuit breaker) and at least two phase terminals supported by the housing and configured to be connected to respective ones of at least two phase buses in an electrical panelboard. The apparatus further includes at least one fault generation device supported by the housing and including an arc containment chamber and first and second spaced-apart electrodes in the arc containment chamber and electrically coupled to respective ones of the at least two phase terminals.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.16/419,627; filed May 22, 2019, the contents of which are incorporatedby reference in its entirety.

BACKGROUND

The inventive subject matter relates to electrical power apparatus andmethods and, more particularly, to protection apparatus for electricalpower equipment.

Arc faults may be caused by a variety of different events, includinginadvertent dropping of metal tools on energized components,misalignment of switch contacts, failure of connections, and failedcable or bus insulation. Arc faults can produce arc flashes withsufficient energy to kill or injure personnel and significantly damageequipment.

Several techniques have been developed to mitigate the effects of arcfaults. For example, equipment enclosures may be designed to containand/or channel arc flash heat and gases to reduce or minimize exposureto personnel. Switchgear and similar equipment may also be equipped withactive devices that may reduce arc flash energy. For example, U.S. Pat.No. 6,724,604 to Shea et al. and U.S. Pat. No. 9,025,299 to Shea et al.describe arc fault mitigation devices that can potentially reduce thelikelihood and severity of personnel injury and equipment damage arisingfrom arc faults.

SUMMARY

Some embodiments of the inventive subject matter provide an apparatusincluding a housing and at least two phase terminals supported by thehousing and configured to be connected to respective ones of at leasttwo phase buses in an electrical panelboard. The apparatus furtherincludes at least one fault generation device supported by the housing.The at least one arc fault generation device includes an arc containmentchamber, with first and second spaced-apart electrodes being disposed inthe arc containment chamber and electrically coupled to respective onesof the at least two phase terminals.

In some embodiments, the apparatus may include first, second and thirdphase buses supported by the housing. The at least two phase terminalsmay include first, second and third phase terminals of respective onesof the first, second and third phase buses configured to be connected torespective first, second and third phase conductors of the panelboard.The at least one fault generation device may include a first faultgeneration device having its first and second electrodes coupled to thefirst and second phase buses, respectively, and a second faultgeneration device having its first and second electrodes coupled to thesecond and third buses, respectively.

Each of the first and second fault generation devices may include anelongate housing and first and second terminals disposed at respectivefirst and second ends of the elongate housing along a longitudinal axisthereof. The first, second and third buses may include first, second andthird bus bars extending in parallel along a direction transverse to thelongitudinal axes of the first and second fault generation devices. Thefirst terminal of the first fault generation device may be connected tothe first bus bar, the second terminal of the first fault generationdevice may be connected to the second bus bar, the first terminal of thesecond fault generation device may be connected to the third bus bar,and the second terminal of the second fault generation device may beconnected to the second bus bar. In some embodiments, the first, secondand third bus bars may be aligned in a first plane and the first andsecond terminals of the first and second fault generation devices may bealigned in a second plane parallel to the first plane. The firstterminal of the first fault generation device may be connected to thefirst bus bar by a first conductive member, the first terminal of thesecond fault generation device may be connected to the third bus bar bya second conductive member, the second terminals of the first and secondfault generation devices may be interconnected by a third conductivemember aligned with the second plane, and the third conductive membermay be connected to the second bus bar by a fourth conductive member.

In some embodiments, each fault generation device may include acylindrical body and first and second end caps covering first and secondends of the body to define the arc containment chamber. The first andsecond electrodes may include respective first and second cylindricalelectrodes extending through respective ones of the first and second endcaps into the arc containment chamber, the first and second electrodeshaving longitudinal axes aligned with a longitudinal axis of the bodyand having a gap therebetween in the arc containment chamber. The faultgeneration device may further include a trigger conductor extendingacross an end of the first electrode in the gap and facing an end of thesecond electrode.

In further embodiments, an apparatus includes a cylindrical body, firstand second end caps covering first and second ends of the cylindricalbody to define an arc containment chamber, first and second cylindricalelectrodes extending through respective ones of the first and second endcaps into the arc containment chamber, the first and second electrodeshaving longitudinal axes aligned with a longitudinal axis of the bodyand having a gap therebetween in the arc containment chamber, and atrigger conductor extending across an end of the first electrode in thegap and facing an end the second electrode. The trigger conductor mayinclude a folded portion including first and second overlapping sectionsoverlying the end of the first electrode and separated from the end ofthe first electrode by an insulator. An insulating sleeve may surroundthe second section of the trigger conductor and the sleeved secondsection of the trigger conductor may separate the first section of thetrigger conductor from the end of the first electrode. The first sectionof the trigger conductor may have a fusing cut formed therein. Theapparatus may further include a control lead coupled to the triggerconductor and accessible from outside of the arc containment chamber.

Still further embodiments provide an apparatus including a housinghaving a molded circuit breaker housing form factor. First, second andthird bus bars are disposed in the housing and have respective terminalsfor connection to first, second and third phase conductors. A firstfault generation device is disposed in the housing and connected betweenthe first and second bus bars. A second fault generation device isdisposed in the housing and connected between the second and third busbars. The first, second and third bus bars may extend in parallel. Thefirst and second fault generation device may each include a cylindricalbody and may be arranged side-by-side with longitudinal axes of thecylindrical bodies arranged transverse to the first, second and thirdbus bars. Each of the first and second fault generation devices mayinclude first and second end caps covering first and second ends of thecylindrical body to define an arc containment chamber. First and secondcylindrical electrodes may extend through respective ones of the firstand second end caps into the arc containment chamber, the first andsecond electrodes having longitudinal axes aligned with a longitudinalaxis of the body and having a gap therebetween in the arc containmentchamber. A trigger conductor extends across an end of the firstelectrode in the gap and facing an end the second electrode.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an arc mitigation device according tosome embodiments of the inventive subject matter.

FIG. 2 is a top view of the arc mitigation device of FIG. 1 .

FIG. 3 is a perspective view of a fault generation device of the arcmitigation device of FIGS. 1 and 2 .

FIG. 4 is a cross sectional view of the fault generation device of FIG.3 .

FIGS. 5-7 are side views of an electrode and trigger conductor structureof a fault generation device according to some embodiments.

FIGS. 8 and 9 are perspective views of the electrode and triggerconductor of FIGS. 5-7 .

FIGS. 10 and 11 are isolated perspective views of the trigger conductorof FIGS. 5-9 .

FIG. 12 is a side view of a trigger conductor arrangement for thetrigger conductor of FIGS. 5-9 .

FIG. 13 is a schematic block diagram of an arc mitigation systemaccording to some embodiments.

FIG. 14 is a perspective view of fault generation devices and bus barsof the arc mitigation device of FIG. 1 .

FIG. 15 is a side view of the fault generation devices and bus bars ofFIG. 3 .

FIG. 16 is a top view of the fault generation devices and bus bars ofFIG. 3 .

FIG. 17 is an end view of the fault generation devices and bus bars ofFIG. 3 .

FIG. 18 illustrates the are mitigation device of FIGS. 1 and 2 with acover installed.

FIGS. 19 and 20 illustrate the arc mitigation device of FIG. 18installed in an electrical panelboard.

DETAILED DESCRIPTION

Specific exemplary embodiments of the inventive subject matter now willbe described with reference to the accompanying drawings. This inventivesubject matter may, however, be embodied in many different forms andshould not be construed as limited to the embodiments set forth herein;rather, these embodiments are provided so that this disclosure will bethorough and complete, and will fully convey the scope of the inventivesubject matter to those skilled in the art. In the drawings, likenumbers refer to like items. It will be understood that when an item isreferred to as being “connected” or “coupled” to another item, it can bedirectly connected or coupled to the other item or intervening items maybe present. As used herein the term “and/or” includes any and allcombinations of one or more of the associated listed items.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the inventivesubject matter. As used herein, the singular forms “a”, “an” and “the”are intended to include the plural forms as well, unless expresslystated otherwise. It will be further understood that the terms“includes,” “comprises,” “including” and/or “comprising,” when used inthis specification, specify the presence of stated features, integers,steps, operations, items, and/or components, but do not preclude thepresence or addition of one or more other features, integers, steps,operations, items, components, and/or groups thereof.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this inventive subject matterbelongs. It will be further understood that terms, such as those definedin commonly used dictionaries, should be interpreted as having a meaningthat is consistent with their meaning in the context of thespecification and the relevant art and will not be interpreted in anidealized or overly formal sense unless expressly so defined herein.

FIGS. 1 and 2 illustrate an arc mitigation device 100 according to someembodiments. The arc mitigation device 100 includes a housing, here ahousing 110 having a form factor substantially similar to that of acircuit breaker, such as an Eaton Series C® molded case circuit breaker.Packaging the arc mitigation device 100 in such a housing may findparticularly advantageous application in providing arc fault mitigationin an electrical panelboard or other equipment at a location suited forinstallation of a standard form factor breaker. It will be appreciatedhowever, that embodiments of the inventive subject matter are notlimited to such a form factor.

The housing supports first and second fault generation devices 120 a,120 b, which are connected to bus bars 130 a, 130 b, 130 c. The bus bars130 a, 130 b, 130 c have respective terminals 132 a, 132 b, 132 c forconnecting the bus bars 130 a, 130 b, 130 c to, for example, respectivebus conductors of an electrical panelboard in which the arc mitigationdevice 100 is installed. The arc-mitigation device 100 can be used, forexample, to mitigate the effects of an arc fault of one or more of thepanelboard buses. For example, responsive to detection of such a fault,contained faults between the buses 130 a, 130 b, 130 c may be createdwithin the fault generation devices 120 a, 120 b, which can potentiallyreduce the amount of damaging heat, pressure waves, shrapnel, soundwaves, intense light, and toxic gases produced by the arc associatedwith the detected fault. As explained below, the fault generationdevices 120 a, 120 b may be triggered responsive to light and increasedcurrent associated with the original fault.

FIGS. 3 and 4 illustrate a fault generation device 120 according to someembodiments. The fault generation device 120 includes a housing 121having a cylindrical body 128 and end cap structures 127 a, 127 b thattogether enclose an arc-containment chamber 123. The cylindrical body128 and end cap structures may be fabricated from a variety of differentmaterials, such as stainless steel. In some embodiments, the housing 121may further include an inner liner 129, which may be, for example, acylindrical member formed a copper-tungsten alloy (e.g., Elkonite®) orother material that provides enhanced strength and resistance tofault-generated heat and pressure.

First and second electrodes 122 a, 122 b are aligned with a longitudinalaxis of the housing 121 pass through the end cap structures 127 a, 127 binto the arc containment chamber 123. Ends of the electrodes 122 a, 122b outside of the chamber 123 may serve as terminals for connecting thefault generation device 120 to bus bars or other external conductors.For example, external ends of the electrodes 122 a, 122 b may beexternally threaded or have threaded holes therein configured to acceptnut or bolts for fastening bus bars or other conductors to the ends ofthe electrodes 122 a, 122 b. However, it will be appreciated that otherterminal arrangements, such as clamping connectors, may be used.

Within the fault-containment chamber 123, a gap is provided between endsof the first and second electrodes 122 a, 122 b. A trigger conductor 126is affixed to one of the electrodes 122 a in this gap and may be used togenerate a fault between the first and second electrodes 122 a, 122 b.In particular, using an external lead 125, a current may be passedthrough the trigger conductor 126, causing the trigger conductor 126 tobridge across the gap, fuse and create an arc fault between theelectrodes 122 a, 122 b.

FIGS. 5-12 illustrate the electrode and trigger conductor structure ingreater detail. Referring to FIGS. 5-12 , an electrode 122 is agenerally cylindrical structure formed of a conductive material,particularly one suited for use in applications involving elevatedtemperatures. For example, the electrode 122 may be formed of anElkonite® material, which are compositions of copper and refractorymetals (e.g., tungsten, molybdenum and tungsten carbide).

A trigger conductor 126 is folded over to form a top section 126 a and abottom section 126 b and is mechanically attached and electricallyconnected to the electrode 122 on a first side thereof using, forexample, a first screw 510 a. The bottom section 126 b is covered by afirst insulating sleeve 520, which isolates the bottom section 126 bfrom the electrode 122. The top section 126 a of the folded triggerconductor 126 passing over the end of the electrode 122 is electricallyisolated from both the bottom portion 126 b and the end of the electrode122 by the first insulating sleeve 520, which covers the bottom section126 b of the trigger conductor 126.

On a second side of the electrode 122, the top section 126 a of thetrigger conductor 126 has a cut 126 c that serves as fusing point (i.e.,a point at which the trigger conductor 126 separates under high currentconditions). Below the fusing point cut 126 c, the top section 126 a ofthe trigger conductor 126 is covered by a second insulating sleeve 530.A second screw 510 b affixes the portion of the trigger conductor 126covered by the second sleeve 530 to the electrode 122 such that the topsection 126 a of the trigger conductor 126 is held against the electrode122 but electrically isolated from the electrode 122 by the sleeve 520.The bottom portion 126 b of the trigger conductor 126 is also heldagainst the electrode 122 by the second screw 510 b but is notelectrically insulated from the electrode 122. The illustrated structuresupports concentration of current through the relatively thin topsection 126 a of the trigger conductor 126 overlying the end of theelectrode 122, thus facilitating the fusing of the trigger conductor126.

It will be appreciated that the trigger conductor 126 is generally asacrificial element that is destroyed by operation of the device. Afteroperation of the device, the trigger conductor 126 can be replaced toenable reuse of the device 120. In particular, the end cap structure 127a can be removed to access the containment chamber 123 to remove debris.Remnants of the used trigger conductor 126 on the electrode 122 a can beremoved by loosening the screws 510 a, 510 b. A new trigger conductor126 and associated insulation components 520 and 530 can then beinstalled using the screws 510 a, 510 b. Damaged ones of the electrodes122 a, 122 b may also be replaced. In particular, the end cap structures127 a, 127 b may be disassembled to allow removal and replacement ofdamaged electrodes 122 a, 122 b.

FIG. 13 illustrates an arc-mitigation system according to furtherembodiments. The system includes first and second fault generationdevices 120 a, 120 b coupled to first second, and third phase conductors1340 a, 1340 b, 1340 c. In particular, the first fault generation device120 a is connected between the first and second phase conductors 1340 a,1340 b and the second fault generation device 120 b is connected betweenthe second and third phase conductors 1340 b, 1340 c. The faultgeneration devices 120 a, 120 b are coupled to a control circuit 1310,which controls currents passing through the trigger conductors of thefault generation devices 120 a, 120 b. The control circuit 1310 operatesresponsive to a protective relay device 1320, which is coupled tocurrent sensors 1330 a, 1330 b, 1330 c that sense current in respectiveones of the first, second and third phase conductors 1340 a, 1340 b,1340 c, and to an arc light sensor 1350, which is configured to detectthe light produced by an arc flash. Responsive to detection of currentlevels and arc flash light associated with an arc fault, the protectiverelay 1320 causes the control circuit to generate a current in thetrigger conductors of the fault generation devices 120 a, 120 b. This,in turn, causes generation of faults within the fault generation devices120 a, 120 b.

FIGS. 14-17 illustrate components of the arc mitigation device 100 ofFIGS. 1 and 2 with the housing 110 absent. The bus bars 130 a, 130 b,130 c are generally elongate bars formed from a conductive material,such as copper or an aluminum alloy. The bus bars 130 a, 130 b, 130 cextend in parallel and generally lie in the same plane underneath thefirst and second fault generation devices 120 a, 120 b. The longitudinalaxes of the first and second fault generation devices 120 a, 120 bgenerally lie in a second plane parallel to the plane of the bus bars130 a, 130 b, 130 c and are oriented transverse to the bus bars 130 a,130 b, 130 c. A first terminal of the first fault generation device 120a is connected to the first bus bar 130 a by a first member 134 a. Afirst terminal of the second fault generation device 120 b is connectedto the third bus bar 130 c by a second conductive member 134 b. Secondterminals of the first fault generation device 120 a and the secondfault generation device 120 b are interconnected by a serpentine thirdconductive member 136, which is connected to the second bus bar 130 b bya fourth conductive member 138.

FIG. 18 illustrates the arc mitigation device 100 of FIGS. 1 and 2according to further embodiments. The device housing 110 includes a baseportion 110 a, which includes a compartment in which the faultgeneration devices 120 a, 120 b and associated bus bar structures arepositioned. The housing 110 further includes a cover 110 b that coversthe fault generation devices 120 a, 120 b and bus structures, thusproviding a unit that has the form factor of a molded case circuitbreaker. As shown in FIG. 18 , the arc mitigation device 100 can bemounted in a panelboard, for example, in a location configured forinstallation of a molded case circuit breaker. The arc mitigation device100 can be designed as a single-use (sacrificial) device that can bereplaced after one operation.

FIGS. 19 and 20 illustrate an example application of an arc mitigationdevice according to some embodiments. A panelboard 1900 may beconfigured to receive a standard form circuit breaker. The panelboard1900 includes a housing 1910 and a bus backplane assembly 1920configured to be mounted within the housing 1910. The bus backplaneassembly 1920 may be configured to receive a circuit breaker, which maybe electrically connected to buses 1922 of the bus backplane assembly1920. An inner cover 1930 may cover the bus backplane assembly 1920 andinclude a cutout sized to expose a front face of a circuit breakerinstalled in the bus backplane assembly. An outer cover 1940 isconfigured to cover the inner cover and the exposed face of theinstalled circuit breaker. As illustrated, according to someembodiments, an arc mitigation device 100 having a form factorsubstantially the same as a circuit breaker may be installed in thepanelboard 1900, instead of a circuit breaker.

In the drawings and specification, there have been disclosed exemplaryembodiments of the inventive subject matter. Although specific terms areemployed, they are used in a generic and descriptive sense only and notfor purposes of limitation, the scope of the inventive subject matterbeing defined by the following claims.

That which is claimed:
 1. An apparatus comprising: a cylindrical body;first and second end caps covering first and second ends of thecylindrical body to define an arc containment chamber; first and secondcylindrical electrodes extending through respective ones of the firstand second end caps into the arc containment chamber, the first andsecond electrodes having longitudinal axes aligned with a longitudinalaxis of the cylindrical body and having a gap therebetween in the arccontainment chamber; and a trigger conductor conforming to and affixedto a sidewall of the first electrode, extending from the sidewall on toan end of the first electrode facing an end of the second electrode. 2.The apparatus of claim 1, wherein the trigger conductor comprises afolded portion comprising first and second overlapping sectionsoverlying the end of the first electrode and separated from the end ofthe first electrode by an insulator.
 3. The apparatus of claim 2,further comprising an insulating sleeve surrounding the second sectionof the trigger conductor and wherein the sleeved second section of thetrigger conductor separates the first section of the trigger conductorfrom the end of the first electrode.
 4. The apparatus of claim 3,wherein the insulating sleeve comprises a first insulating sleeve andfurther comprising a second insulating sleeve surrounding a portion ofthe first section conforming to the sidewall of the first electrode andelectrically isolating the sleeved portion of the first section from thefirst electrode.
 5. The apparatus of claim 2, wherein the first sectionof the trigger conductor has a fusing cut formed therein.
 6. Theapparatus of claim 2, wherein first and second ends of the first andsecond overlapping sections extend onto opposite sidewalls of the firstelectrode and are affixed thereto.
 7. The apparatus of claim 1, furthercomprising a control lead coupled to the trigger conductor andaccessible from outside of the arc containment chamber.